I'm doing software development professionally and as a hobby for over 30 years now. And OpenSource software for almost as long, hence a a lot of my stuff can be found on the Interwebs, e.g. on GitHub.
Business
  ZeeZide / Freelance:
  Working on projects/products for ZeeZide GmbH,
  as well as doing freelance work.
  If you got some interesting project, feel free to
  contact me.
  
  
    Timeframe:    2015-today
    Technologies:
    SwiftUI,
    SwiftNIO,
    and more.
  
  Undisclosed:
  Major car manufacturer.
  Owning/developing a Swift SDK for secure communication with a headunit over 
  CarPlay
  protocols.
  Protoyping various car automation features.
  
  
  
    Timeframe:    Aug 2022-Dec 2023
    Technologies:
    CarPlay,
    External Accessory framework,
    Network.fwk,
	Siri Intents,
	Apple Maps.
  
  Undisclosed:
  Helped a startup implement an iOS
  Network Extension,
  including a Network.framework based HTTP proxy.
  
  
    Timeframe:    Nov 2021
    Technologies:
    Network Extension,
    Network.fwk,
    http_parser,
    SQLite.
  
  Undisclosed:
  Major car manufacturer.
  Implemented a Swift SDK for secure communication with a headunit over 
  CarPlay
  protocols.
  
  
  
    Timeframe:    Sep/Oct 2021
    Technologies:
    CarPlay,
    External Accessory framework,
    Network.fwk.
  
  Past for iChat.app:
  Simple but fancy viewer for iChat chat log files on macOS Big Sur.
  Written in SwiftUI.
  
  
    Timeframe:    2021
    Technologies:
    SwiftUI,
    QuickLook,
    Swift.
  
  Battery Status for HomeMatic.app:
  Simple iPhone app reporting on the battery of
  HomeMatic home automation devices.
  
  
    Timeframe:    2021
    Technologies:
    SwiftUI,
    HomeMatic,
    Swift.
  
  Shrugs.app:
  A native macOS client for the Slack messaging service.
  Written in Swift, using UXKit/AppKit.
  
  
    Timeframe:    2018-today
    Technologies:
    Slack API,
    AppKit,
    UXKit,
    Swift.
  
  HMScriptEditor:
  A macOS app for testing and running
  HomeMatic scripts.
  
  
    Timeframe:    Q4 2018, Nov 2021
    Technologies:
    HomeMatic,
    AppKit,
    SwiftUI.
  
  Undisclosed:
  Helped a tech startup to implement a roaming solution,
  primarily working on the iOS SDK and the iOS application parts.
  Server side Swift running on the client, yay!
  
  
    Timeframe:    2016-2018
    Technologies:
    Noze.io,
    Swift,
    UIKit
  
  Apple/iCloud:
  CalDAV/CardDAV client for Microsoft Outlook,
  Chrome bookmarks syncing extension.
  
  
    Timeframe:    2010-2013
    Technologies:
    CalDAV,
    CardDAV,
    C,
    C++,
    SQLite,
    MAPI
  
  Outlook plugin:
  
  I worked on building a
  MAPI message store provider
  for
  Microsoft Outlook
  which stores Outlook entities into
  
  GroupDAV
  / CalDAV
  / CardDAV
  
  capable WebDAV servers.
  
  Well, ZideOne has ceased operations. Don't ask.
 
  
  
    Timeframe:    2007-2009
    Technologies:
    C,
    C++,
    SQLite,
    MAPI,
    GroupDAV,
    WebDAV,
    CalDAV
  
  Chamber Management System:
  
  I design and lead the development of a web based management system
  for a chamber of pharmacists in Germany. The system is built
  in Java on top of OpenGroupware.org technology.
  
  
  
    Timeframe:    Nov 2007-Jul 2009
    Technologies:
    OGo,
    Go,
    OpenOffice.org,
    Java
  
  OpenGroupware.org:
  
  For
  SKYRIX Software AG
  I architect, implement and maintain extensions to the OGo groupware
  server.
  This includes work across all layers of OGo, from the application
  logic through protocol layers up to the web interface.
  
  
    Timeframe:    1996-2008
    Technologies:
    C,
    Objective-C,
    Linux,
    PostgreSQL,
    SOPE
  
  SMS/MMS Platform:
  
  An enterprise scale SMS/MMS transaction and service platform which is
  in use by various large media customers, MNOs and SMEs.
  My primary work is on system reliability, mobile handset detection and
  on-the-fly MMS repurposing.
  
  
  
    Timeframe:    Feb 2006-Sep 2007
    Technologies:
    MMS,
    SMIL,
    C,
    Objective-C,
    Java,
    Tomcat,
    Linux,
    PostgreSQL
  
  PostgreSQL Cluster:
  
  To secure the data in a large scale deployment of electronic
  datarooms
  we configured a
  PostgreSQL
  warm standby replication cluster using the write ahead logging
  facility of the server.
  The datarooms are accessed using a set of
  Ruby on Rails
  web applications.
  
  
  
    Timeframe:    Apr-Aug 2007
    Technologies:
    PostgreSQL,
    Ruby on Rails
  
  Card Management System:
  
  For a large German trust center I architect and lead the development of
  a system to securely manage applications for qualified signature /
  encryption cards (health professional cards).
  Prototypes implemented in SOPE, later moved to Java/Go.
  
  
  
    Timeframe:    Feb 2004-Apr 2007
    Technologies:
    Java,
    Jetty,
    Go,
    SOPE,
    HPC,
    Smartcards,
    OpenSSL,
    MySQL
  
  Agenor:
  
  For a large French ministry I designed and led the development of a
  massively scalable groupware server. Designed to serve 60.000 ministry
  workers.
  The project kicked off the ScalableOGo OpenSource project which is currently
  being continued by Inverse.
  
  
  
    Timeframe:    2004-2005
    Technologies:
    C,
    Objective-C,
    PostgreSQL,
    GroupDAV,
    WebDAV,
    CalDAV
  
  Instant OGo:
  
  Designed and implemented an administration web interface for various
  Linux services. A proprietary OGo component which is in use in the
  excellent
  Instant-OGo
  product.
  
  
  
    Timeframe:    2003
    Technologies:
    OGo,
    Objective-C,
    Linux,
    SOPE
  
  SKYRiX Publisher:
  
  Enhanced the SKYRIX web application server (now OGo) with an enterprise
  content management system. Was in use at a large plant research institute
  to maintain thousands of documents in a structured way.
  
  
  
    Timeframe:    2002
    Technologies:
    OGo,
    Objective-C,
    SOPE,
    Content Management
  
OpenSource / Sparetime
  Lighter.swift:
  A set of technologies applying code generation to access 
  SQLite3 
  databases from 
  Swift, 
  e.g. in iOS applications or on the server. Like SwiftGen but for SQLite3.
  Super fast and fully typesafe.
  
  
    Timeframe:    Apr 2022
    Technologies:
    SQLite,
    Swift Package plugins.
  
  ViewController:
  An approach to deal with application/navigation state within SwiftUI
  applications. Present as you used to!
  
  
    Timeframe:    Apr 2022
    Technologies:
    SwiftUI,
    MVC.
  
  docc2html:
  Swift package to read 
  DocC 
  archives and a tool to export them as a static website.
  
  
    Timeframe:    Jul 2021
    Technologies:
    DocC,
    Swift.
  
  Mio:
  A macOS port of the
  Nio chat
  client for Matrix.
  
  
    Timeframe:    Mar 2021
    Technologies:
    Matrix,
    SwiftUI,
    Swift.
  
  NWHTTPProtocol:
  An HTTP protocol parser (aka NWProtocolFramer) for the 
  Apple Network.framework, an implementation of the
  Transport Services API (taps)
  in Swift.
  
  
    Timeframe:    Oct 2020
    Technologies:
    Network.framework,
    taps,
    http_parser,
    Swift.
  
  5 GUIs:
  A tiny macOS SwiftUI app that can detect the GUI technologies used in other 
  apps, i.e. whether they use Electron, AppKit, Catalyst, etc.
        
  
  
    Timeframe:    Oct 2020
    Technologies:
    LLVM,
    SwiftUI
  
  SwiftBlocksUI:
  Slack
  can be enhanced with
  interactive dialogs and dynamic messages.
  Buttons, Pickers, TextFields and more.
  SwiftBlocksUI
  is
  SwiftUI
  for Slack applications.
        
  
  
    Timeframe:    July 2020
    Technologies:
    Slack API,
    SwiftUI,
    Swift.
  
  Direct to SwiftUI:
  An adaption of an old 
  WebObjects
  technology called 
  Direct to Web for
  SwiftUI.
  Instant CRUD
  apps, configurable using 
  a declarative rule system,
  yet fully integrated with SwiftUI.
  
  
    Timeframe:    August 2019
    Technologies:
    SwiftUI,
    Swift,
    DirectToWeb.
  
  SwiftUIRules:
  SwiftUIRules
  adds a declarative rule system to the
  SwiftUI
  Environment feature.
  Think: Cascading Style Sheets or Direct to Web for SwiftUI.
  
  
    Timeframe:    August 2019
    Technologies:
    SwiftUI,
    Swift,
    DirectToWeb.
  
  SwiftWebUI:
  At 
  WWDC 2019
  Apple announced 
  SwiftUI.
  SwiftWebUI
  is bringing that to the Web ✔️:
  The missing ☑️.
  
  
    Timeframe:    June 2019
    Technologies:
    SwiftUI,
    Swift NIO,
    Swift
  
  SwiftPM Catalog.app:
  A macOS frontend to the
  Swift Package Index.
  
  
    Timeframe:    Q4 2018
    Technologies:
    SwiftPM,
    AppKit,
    UXKit,
    Swift.
  
  SwiftObjects:
  An experiment to figure out how the
  WebObjects
  API might look like in
  Swift.
  
  Also:
  An Introduction to WebObjects, in Swift.
  
  
    Timeframe:    June 2018
    Technologies:
    WebObjects,
    Swift NIO,
    Swift
  
  SwiftyLinkerKit:
                                
  This is an easy way to work with 
  LinkerKit
  components in 
  Swift.
  Includes
  SwiftyTM1637,
  a driver for the TM1637 7-segment chip,
  as well as an IRC 
  LinkerKit chat bot.
  
  
    Timeframe:    Jun 2018
    Technologies:
    LinkerKit,
    SwiftyGPIO,
     Raspberry Pi,
    Swift
  
  swift-nio-irc:
  SwiftNIO IRC
  is a
  Internet Relay Chat (IRC)
  protocol implementation for 
  Swift NIO,
  a basis for building your own IRC servers, clients and bots,
  a sample IRC server
  (including a web client),
  as well as 
  some IRC bots,
  written in the 
  Swift
  programming language.                                
  
  
    Timeframe:    2018-today
    Technologies:
    Swift NIO,
  IRC,
    Swift,
    WebSockets
  
  swift-nio-redis ✭
                              Redi/S:
  Includes a
  RESP
  protocol implementation for 
  Swift NIO,
  a convenient
  Redis client library
  for Swift,
  and a fast Redis server written in Swift:
  Redi/S.
  
  
    Timeframe:    2018-today
    Technologies:
    Swift NIO,
    Redis,
    Swift
  
  µExpress:
  A tiny but useful Express-like web framework built upon
  Swift NIO,
  the new async-IO Swift framework by Apple.
  Popular blogpost in which we build µExpress:
  A µTutorial on Swift NIO.
  
  
    Timeframe:    2018-today
    Technologies:
    Swift NIO,
    Swift
  
  SwiftXcode:
  Use
  Swift Package Manager
  directly within in Xcode.
  Ready-to-go Xcode templates for 
  iOS apps, macOS tools, SwiftNIO and Kitura.
  No more swift package generate-xcodeproj!
  
  
    Timeframe:    2018-today
    Technologies:
    Xcode,
    Swift Package Manager
  
  PL/Swift:
  Custom SQL functions and types for the PostgreSQL database server,
  written in the Swift programming language.
  That is what PL/Swift does.  
  
  
    Timeframe:    2018-today
    Technologies:
    PostgreSQL Extensions,
    Swift
  
  UXKit:
  Write code that works on both, UIKit and AppKit.
  Not only useful for deployment to macOS, but during development, 
  reduce simulator/device testing annoyances.
  Drives
  CodeCows
  /
  ASCII Cows.
  
  
  
    Timeframe:    2017-today
    Technologies:
    UIKit,
    AppKit, 
    Swift
  
  Swift Server Project HTTP APIs:
  Wrote a 
  GCD based, asynchronous implementation
  of the proposed, official Swift Server API.
  Maybe this gets pulled, maybe not. Probably not :-)
  
  
  
    Timeframe:    2017
    Technologies:
    GCD,
    Swift
  
  ApacheExpress:
  mod_swift
  on steroids.
  Host Swift within Apache, that is, reliably :-)
  Stay tuned, a preview is available, but something bigger is in the works.
  
  
  
    Timeframe:    2017-today
    Technologies:
    Swift,
    Apache,
    mod_dbd
  
  VueXcode:
Want to edit Vue components in Xcode, but they just show up in black&white? Trying to change the file type using the 'Type' popup, but Xcode can't remember? Use VueXcode.
  
  
    Timeframe:    2017
    Technologies:    
    Swift,
    Vue.js
    AppKit, Xcode, Cocoa
  
  ZeeQL:
  Standalone Swift ORM / database access library primarily inspired by EOF, 
  and in consequence CoreData, adding some ActiveRecord concepts.
  Can be used on Swift server, mobile or desktop.
  
  
    Timeframe:    2017-today
    Technologies:
    Swift,
    EOF, CoreData,
    SQLite3,
    PostgreSQL,
    mod_dbd
  
  dockSwiftOnARM:
  Docker images
  for the Swift programming language
  that work on ARM platforms, specifically the
  RaspberryPi.
  Including Server Side Swift via
  mod_swift.
  
  
  
    Timeframe:    2017-today
    Technologies:
    Swift,
    Docker,
    RaspberryPi
  
  mod_swift:
  A toolkit to write native Apache modules in Swift.
  Includes a subset of the Connect/Express framework of
  Noze.io
  which makes it very easy to write modules.
  Instead of reinventing the HTTP server, hook into something that just works 
  and is battle proven.
  
  
  
    Timeframe:    2017-today
    Technologies:
    Swift,
    Apache,
    JSON, HTTP
  
  Noze.io:
  The "Server Side Swift aS a Service" toolkit 😉
  Noze.io are Node.js-like, evented I/O streams for Swift.
  Implements core Node modules like leftpad, net or http,
  as well as some external ones, like Connect and Express.
  
  
  
    Timeframe:    2015-2017
    Technologies:
    Swift,
    GCD,
    JSON, HTTP, Streaming
  
  SwiftSockets, 
     SwiftyHTTP,
     SwiftyExpat:
  
  SwiftSockets is kind of a demo on how to integrate Swift
  with raw C APIs.
  More for stealing Swift coding ideas than for actually
  using the code in a real world project.
  It also comes with a great Echo daemon as a demo, it's
  always there if you need a chat.
  
  
  
    Timeframe:    2014-2016
    Technologies:
    Swift,
    GCD,
    Expat, XML, HTTP
  
  Go:
  
  Go is a set of Java frameworks to build powerful Ajax, web and web service
  applications. Comes with a lot of WebObjects compatibility as well as
  support for Zope concepts.
  
  
  
    Timeframe:    2005-2010, 2014-today
    Technologies:
    Java,
    Tomcat,
    Jetty,
    Eclipse,
    JDBC, HTML,
    WebObjects,
    Zope
  
  ScalableOGo:
  
  A groupware server designed for massive scalability. The result of the
  Agenor project. This is a completely stateless application with a novel
  storage concept which allows high scalability despite using a RDBMS
  storage backend. For 60.000+ users.
  
  
  
    Timeframe:    2004-2009
    Technologies:
    GroupDAV,
    PostgreSQL,
    SOPE,
    Objective-C
  
  GroupDAV:
  
  During a
  KDE/OGo meeting
  we designed a new groupware protocol to allow the lots of OpenSource
  groupware servers to connect to OpenSource groupware clients.
  
  
  
    Timeframe:    Dec 2004-2009
    Technologies: WebDAV, iCalendar, vCard, Calendaring
  
  OpenGroupware.org:
  
  I'm the project lead of
  OGo
  and coordinate the small but excellent community. Doing talks on
  various events.
  Currently working on the Java port of OGo, OGo/J.
  
  
  
    Timeframe:    1996-2009
    Technologies:
    C,
    Objective-C,
    Linux,
    PostgreSQL,
    SOPE
  
  SOPE:
  
  Initially a clone of the WebObjects 4.5.1 web application framework, 
  SOPE was enhanced with concepts from the modern Zope environment.
  SOPE is the application server used by OGo as well as SOGo.
  Includes a large collection of modules:
  XML parsers, iCalendar/vCard processing, NIO streams, EOControl,
  MIME/IMAP4 support, LDAP wrappers, database drivers, the appserver
  itself, etc
  
  
  
    Timeframe:    1996-2009
    Technologies: Objective-C, HTML, WebObjects, Zope,
    Database C Libraries,
    MIME, IMAP4, LDAP, EOF, XML-RPC, SOAP, SAX, DOM
  
  Remote iTunes:
  
  Prototyped a small application to use the Nokia 770 as a remote
  control for iTunes running on an iMac.
  
  
  
    Timeframe:    2005
    Technologies:
    Maemo,
    Linux,
    AppleEvents, Cocoa,
    Objective-C
  
  libFoundation:
  
  A clone of the OpenStep Foundation library, similar to gnustep-base.
  Initially developed by Ovidiu Predescu and friends. Took over maintenance
  around 2000. Worked on adding support for garbage collection.
  
  
  
    Timeframe:    1996-2009
    Technologies: GCC, Objective-C, Boehm-GC
  
  GNUstep:
  
  Worked on various GNUstep subprojects. Improved the gnustep-make library,
  assisted the creation of the GSWeb framework, enhanced the GNUstep database
  library with additional adaptors and features. Bugfixes in the base library.
  
  
  
    Timeframe:    1996-2009
    Technologies: GCC, Objective-C, Make
  
  libobjc:
  
  Designed and assisted implementation of garbage collection support for
  GNU Objective-C in cooperation with Ovidiu.
  
  
  
    Timeframe:    1997
    Technologies: C, ObjC Runtime, GCC
  
  GTKKit:
  
  Implemented an Objective-C wrapper around the GNOME gtk+ GUI library.
  Modelled after AppKit where possible, integrated NSRunLoop with the X11/GDK
  event handling.
  
  
  
    Timeframe:    1998
    Technologies: C, gtk+, X-Windows
  
  Apache ObjC:
  
  An Apache module to enhance the server with regular Objective-C
  NSBundle packages.
  
  
  
    Technologies: Apache API, C, ObjC runtime
  
  NGPython:
  
  Wrote an Objective-C / Python bridge for use in the Skyrix 3 web application
  server. Full support for Java-Bridge like 'jobs' files and a Pythonic API
  to Objective-C.
  
  
  
    Timeframe:    1998-2000
    Technologies: CPython Embedding, ObjC runtime
  
  NGJavaScript:
  
  Wrote an Objective-C / JavaScript bridge for use in the form engine of the
  Skyrix 4 server. Allowed users to write small applications using HTML and
  JavaScript inside the groupware system.
  
  
  
    Timeframe:    2000-2003
    Technologies: C, ObjC Runtime, Mozilla SpiderMonkey
  
  mod_ngobjweb:
  
  A non-streaming Apache module to forward HTTP requests to backend application
  servers. Capable to distribute requests across cluster nodes with a central
  registry daemon (snsd). Support for sessions stored in volatile memory.
  Now part of SOPE.
  
  
  
    Timeframe:    1996-2009
    Technologies: C, Apache 1/2 API
  
  CocOOo:
  
  Small AppKit application to view OOo files. Loads the XML stored in
  the OOo file, transforms it into HTML which is then displayed in a
  WebKit view.
  
  
  
    Timeframe:    2003
    Technologies: AppKit, WebKit, OpenDocument Format, XSLT, Objective-C